This application claims benefit of Japanese Applications No. H11-359500 filed on Dec. 17, 1999, No. H11-359501 filed on Dec. 17, 1999, No. H11-359502 filed on Dec. 17, 1999, and No. H11-359503 filed on Dec. 17, 1999, the contents of which are incorporated by this reference.
1. Field of the Invention
This invention relates to a finder unit, and more particularly to a finder unit, having a finder optical system, for verifying and observing a field-of-view range containing a desired photographic image, in a camera or the like for taking pictures or the like.
2. Description of the Related Art
Various real-image type finder units have been proposed, as in Japanese Patent Application Laid-Open No. H10-10440/1998, for example, and made generally practical, which are finder units for verifying and observing a field-of-view range containing a desired viewing image, in a camera or the like for taking pictures or the like, that have a finder optical system configured by an objective optical system, inverting optical system, and eyepiece optical system, configured such that the viewing image formed by the objective optical system is made an erecting normal image by the inverting optical system, and enlarged for viewing by the eyepiece optical system.
The finder optical system of the finder unit disclosed in Japanese Patent Application Laid-Open No. H10-10440/1998 is made so that, by displacing the interval between the image formation position of the viewing image formed by the objective optical system and the condenser lens close to the eyepiece optical system by a prescribed distance (more than approximately 4 diopters (1/m)), the dust, grime, and scratches on the surface, etc., of the condenser lens and the dust and the like inside the prism will not be observed. This [finder optical system] is thus such that a good viewing image can be obtained.
Nevertheless, in the finder unit disclosed in Japanese Patent Application Laid-Open No. H10-10440/1998 (published), although it is possible to make the configuration such that dust and grime and the like adhering to the surface of the optical components (condenser lens) on the eyepiece optical system side that is in opposition to the viewing image formation position are not observed, there is no mention whatever of the similar problem in the optical components of the objective optical system in opposition to that image formation position.
Meanwhile, for conventional real-image type finder units such as described above which comprise a visibility adjustment mechanism wherewith the user of the unit can adjust the viewing visibility of the finder optical system at his or her discretion, various proposals have been made in the past, such as for means configured so that the viewing visibility can be altered by moving at least one optical component (specifically, the eyepiece lens, etc., configuring part of the eyepiece optical system) of the finder optical system, and these have been made generally practical.
However, when consideration is given to employing, in the finder optical system of the finder unit disclosed in Japanese Patent Application Laid-Open No. H10-10440/1998 (published), noted earlier, a visibility adjustment mechanism wherewith the viewing visibility is adjusted by moving the eyepiece lens, the problems discussed below are encountered.
That is, in the finder optical system of the finder unit disclosed in Japanese Patent Application Laid-Open No. H10-10440/1998 (published), the arrangement of the [configuring] members is set so that the interval between the image formation position for the viewing image formed by the objective optical system and the condenser lens close to the eyepiece optical system is displaced a prescribed distance.
In the finder unit of Japanese Patent Application Laid-Open No. H10-10440/1998 (published) noted above, when the configuration is made so that the interval between the image formation position of the viewing image and the condenser lens is displaced by approximately 4 diopters (1/m), it is possible to view a viewing image that is appropriate to a person with normal vision. However, when used in this condition by a near-sighted or far-sighted person, it is not possible to view an appropriate viewing image.
That being so, consideration is given to providing a visibility adjustment mechanism wherewith appropriate viewing images can be viewed with the same unit by various individuals having respectively different visual acuity. Then, when this is used to move the eyepiece lens of the finder optical system in the direction of the optical axis of the finder optical system, by prescribed means, it becomes possible to adjust the viewing visibility. Thereupon, when a far-sighted person, for example, has used the visibility adjustment mechanism to adjust the viewing visibility so as to be appropriate for himself or herself, the eyepiece lens will be set in a position that is distanced from the viewing image as compared to the position at which a person of normal vision views. Accordingly, should a person of normal vision view a viewing image in this condition, as is, without making a readjustment, it is possible that he or she would be able to observe the dust and grime, etc., adhering to the surface, etc., of the condenser lens.
In other words, there is a problem in that, even when the means disclosed in Japanese Patent Application Laid-Open No. H10-10440/1998 (published) are augmented by a visibility adjustment mechanism, there is no guarantee that it will always be possible to obtain a good viewing image.
Other conventional real-image type finder units are also disclosed, as, for example, in Japanese Patent Application Laid-Open No. H10-307315/1998 (published).
The finder unit disclosed in Japanese Patent Application Laid-Open No. H10-307315/1998 (published) is a so-called bright-frame-finder unit that is configured by a plurality of optical elements, wherein, by deploying a translucent reflecting surface at a prescribed position in the light path of the finder optical system, means for displaying various kinds of information relating to photographing that are superimposed on the viewing image of a desired photographic subject, such as, for example, field of view frame information for-defining the field of view constituting the photographic range, or field of view information for displaying camera settings and operating conditions and the like in a form that can be visually distinguished (hereinafter called in-finder display), are deployed separately from the finder optical system.
In the configuration of the finder unit disclosed in the publication just cited, furthermore, light measuring means for performing light measuring operations for automatically setting the exposure are provided, and light flux division means are provided for making it possible to guide the light flux guided into the interior of the finder unit for those light measuring means and for the means for making the in-finder display described above, respectively. Thus it becomes possible, while viewing the viewing image of the photographic subject, to execute a prescribed light measuring operation using light flux equivalent to the light flux forming that viewing image and to set the exposure at the time of the shooting.
In general, in a bright-frame-finder unit, a display panel is used as means for effecting various kinds of displays in the finder, but this display panel must be deployed at a position that is substantially optically equivalent relative to the positional relationship between the eyepiece optical system and the image formation position of the viewing image formed by the objective optical system.
Based on the means disclosed in Japanese Patent Application Laid-Open No. H10-307315/1998 (published) noted earlier, however, in view of the fact that the configuration is such that there is a plurality of reflecting surfaces between the eyepiece optical system and the image formation position of the viewing image formed by the objective optical system, it is necessary to secure a long distance between the eyepiece optical system and the viewing image formation position. Accordingly, the distance between the eyepiece optical system and the display panel (a liquid crystal display panel in the finder unit disclosed in Japanese Patent Application Laid-Open No. H10-307315/1998 (published)) to be deployed at a position that is substantially optically equivalent relative to the distance between the eyepiece optical system and the viewing image formation position must of necessity be an equivalently long distance. Accordingly, with the means disclosed in Japanese Patent Application Laid-Open No. H10-307315/1998 (published), the finder unit itself becomes large, which is a problem.
Moreover, in order to make it easy to view the viewing image formed by the objective optical system, in a conventional finder unit, the finder magnification power is sometimes set high. For that purpose, various means are ordinarily employed, such as the means of configuring each of the optical elements themselves that configure the finder optical system of large elements, for example, or innovative means of deploying the eyepiece optical system so that the focal length of the eyepiece optical system, that is, the distance between the eyepiece optical system and the viewing image formation position, becomes short.
However, when each of the optical elements themselves becomes large, as in the former case, the finder unit that is configured thereby will itself also become large, wherefore such cannot be called desirable means.
And when the focal length of the eyepiece optical system is made short, as with the latter means, restrictions are imposed when forming the inverting optical system, wherefore there are limitations in making the focal length of the eyepiece optical system short, which is a problem.
In the finder units employed in conventional cameras and the like, furthermore, units have been practically implemented which are configured such that it is possible to view, simultaneously with the viewing image, various kinds of information and the like relating to the photographic shooting, such as field of view frame information for defining the field of view constituting the photographic range, for example, or various kinds of information relating to the photographic shooting for displaying camera settings and operational conditions and the like in such form that they can be visually distinguished (hereinafter called in-finder display). In such cases, in order that the viewing image and the various kinds of photographic shooting information (in-finder display) can be viewed simultaneously, means can be conceived for deploying the display means for displaying the in-finder display of the various kinds of photographic information and the like in the vicinity of the viewing image formation position.
However, when, in the finder unit disclosed in Japanese Patent Application Laid-Open No. H10-10440/1998 (published), the display means for the in-finder display are deployed in the vicinity of the image formation position, it is conceivable that the dust and grime, etc., adhering to the surface, etc., of those display means will be clearly observed.
Thereupon, various means for making it possible to simultaneously view the viewing image and the in-finder display, deploying the display means at a position that is substantially optically equivalent to the image formation position, without deploying the display means in the vicinity of the viewing image formation position, have been proposed, as in Japanese Patent Application Laid-Open No. H10-307315/1998 (published), for example, and made practical.
In Japanese Patent Application Laid-Open No. H10-307315/1998 (published) is disclosed a so-called bright-frame-finder unit that is formed by a plurality of optical elements, as described earlier, configured such that, by deploying a translucent reflecting surface in the light path of the finder optical system, means for displaying various kinds of photographic information and the like superimposed on the viewing image of the desired photographic subject are deployed separately from the finder optical system.
However, the means disclosed in Japanese Patent Application Laid-Open No. H10-307315/1998 (published) are configured such that the prescribed display means are illuminated, receiving only the natural light inducted into the interior of the finder unit from the light-intaking window. Accordingly, when using a finder unit employing those means, there is a problem in that it becomes very difficult to view the in-finder display when the brightness of the surrounding environment is low.
Furthermore, in Japanese Patent Application Laid-Open No. H10-307315/1998 (published), no problems are pointed out and no resolving measures or the like are mentioned whatsoever concerning the possibility of dust and grime, etc., adhering to the surface of a lens deployed in the vicinity of the viewing image formation position being viewed.
The present invention was devised with the points described in the foregoing in view.
A first object of the present invention is to provide a real-image type finder unit wherewith the desired viewing image can always be viewed in a favorable condition and wherewith also smaller size can be realized.
A second object of the present invention is to provide a real-image type finder unit wherewith, even when a visibility adjustment mechanism is comprised, the viewing image can always be viewed in a favorable condition.
A third object of the present invention is to provide a real-image type finder unit having a light-intaking window, wherewith, by innovatively situating the translucent reflecting surface deployed in the interior of the inverting optical system configuring part of the finder optical system, and setting the focal length of the eyepiece optical system so that it is shorter, it is possible both to secure the necessary finder magnification power, and to contribute to the miniaturization of the unit itself by making the finder optical system smaller.
A fourth object of the present invention is to provide a finder unit wherewith it is possible to view an in-finder display of various kinds of photographic information and the like simultaneously with the viewing image containing the desired photographic subject, wherein provision is made so that dust and grime, etc., adhering to the surface, etc., of the optical elements (lenses, etc.) deployed in the vicinity of the viewing image formation position are not viewed, such that a good viewing image can be obtained, wherewith clear viewing of the in-finder display is rendered easy even in low brightness conditions.
Described simply, a first invention is a finder unit including an objective optical system for forming a viewing image, an inverting optical system for making the viewing image formed by the objective optical system an erecting normal image, an eyepiece optical system for viewing the viewing image, a first optical component deployed more toward the side of the objective optical system from the viewing image formation position, and a second optical component deployed more toward the side of the eyepiece optical system from the viewing image formation position, wherein, when the focal length of the eyepiece optical system is represented as f (mm), the distance from the viewing image formation position to the first optical component as D1 (mm), and the distance from the viewing image formation position to the second optical component as D2 (mm), the condition
8 less than 1000xc3x97(D1+D2)/f2(1/m)
is satisfied.
A second invention is a finder unit including an objective optical system for forming a viewing image, an inverting optical system for making the viewing image formed by the objective optical system an erecting normal image, an eyepiece optical system for viewing the viewing image, a visibility adjustment mechanism for adjusting the viewing visibility for the viewing image within a prescribed range, a first optical component deployed more toward the side of the objective optical system from the viewing image formation position, and a second optical component deployed more toward the side of the eyepiece optical system from the viewing image formation position, wherein, when the focal length of the eyepiece optical system is represented as f (mm), the distance from the viewing image formation position to the first optical component as D1 (mm), the distance from the viewing image formation position to the second optical component as D2 (mm), the amount of adjustment of the visibility adjustment means toward the visibility minus side as X1 (1/m), and the amount of adjustment of the visibility adjustment means toward the visibility plus side as X2 (1/m),
the conditions
4+X1 less than 1000xc3x97D1/f2,
and
4+X2 less than 1000xc3x97D2/f2 
are both satisfied.
These and other objects and benefits of the present invention will be made even clearer by the following detailed description.
Based on the present invention, a real-image type finder unit can be provided wherewith a desired viewing object can always be viewed in a favorable condition and smaller size can be realized.
Based on the present invention, moreover, an real-image type finder unit can be provided wherewith, even when equipped with a visibility adjustment mechanism, a desired viewing object can always be viewed in a favorable condition.
In addition, based on the present invention, a real-image type finder unit that has a light-intaking window can be provided wherewith, by innovatively situating a translucent reflective surface deployed in the interior of the inverting optical system configuring part of the finder optical system and making the focal length of the eyepiece optical system shorter, it is possible to secure the necessary finder magnification power and, also, by making the finder optical system smaller, to contribute to making the unit itself smaller.
Based on the present invention, furthermore, a finder unit is provided wherewith it is possible to view an in-finder display of various kinds of photographic information, etc., simultaneously with the viewing image containing the desired photographic subject, made so that dust and grime and the like adhering to the surface, etc., of the optical element (lenses, etc.) deployed in the vicinity of the viewing image formation position are not viewed, such that a good viewing image can be obtained, wherewith also the clear viewing of the in-finder display is rendered easy even under low brightness conditions.